Twenty one Vietnamese people have been arrested in Indonesia for illegally logging rare wood in a protected forest, the Jakarta Post quoted Indonesian police as saying Monday.

Police Chief Adj. Sr. Comr. Trisno Rianto said in the newspaper that the Vietnamese were caught with a vehicle filled with agarwood (Aquilaria crassna) when they left the forest in Aceh province on Sunday.

He said the Vietnamese had been collecting the wood in the forest since early last month.

Six of them were arrested for illegal logging while 15 others would be handed over to immigration officials for violating their tourist visas, according to the official.

Agarwood is mostly sought for its dark resinous heartwood which forms when the tree becomes infected with a type of mold. The heartwood is usually used to make incense and perfumes, but many people believe it can bring good luck to its owners and treat some incurable diseases.